In recent years, a circuit breaker with enlarged capacity is developed along with development of high-voltage and high-current electric power system. On the other hand, there are increasing needs for cost reduction and space saving by optimization of a breaker part structure. Accordingly, a circuit breaker in which puffer gas pressure is higher in comparison with conventional circuit breakers, typified by a small heat puffer type circuit breaker having excellent breaking performance, is being propagated.
Generally, in a breaker-part moving side structure of the gas circuit breaker including the heat puffer type circuit breaker, an insulating nozzle and a moving side main contact are provided on the breaker part side from a puffer cylinder part. The insulating nozzle is provided for the purpose of effectively blowing arc extinguishing gas to arc which occurs between moving side and fixed side arc contacts.
As a typical insulating nozzle fixing method, known is a structure where an outer peripheral part of a rear end of the insulating nozzle is cut in a screw, and is screwed with an inner peripheral screw part at the end of the puffer cylinder from the breaker part side, thus fixing is made.
In this fixing method, it is possible to simply perform attachment and centering work at the time of assembly. Further, upon nozzle change at the time of maintenance, it is possible to perform work from a manhole provided in the vicinity of the breaker part.
However, in accordance with increment in the above-described puffer gas pressure, a holding function with respect to the puffer gas pressure cannot be expected only with the screw fixing structure. Accordingly, the problem is that the potential of accident such as drop off of insulating nozzle upon breaking operation is high.
Regarding such problem, as shown in FIG. 1 of Patent Document 1, a structure to prevent drop off of the insulating nozzle is proposed. The insulating nozzle is engaged with the inner diameter side at the end of the puffer cylinder, and is held with a nozzle presser which also works as a moving side main contact.
In this structure, the insulating nozzle is firmly fixed in comparison with the above-described fixing structure with screw holding, and the drop off of the insulating nozzle due to gas pressure increasing is prevented.